Although Petrolul Ploieşti has been in my heart for more than a decade, I'm still not convinced I'd like to see them back in the 1st League. The reason is their stadium. It's very poor and this is why they play in another town for the time being (Moreni, which is in another county!). And there are no plans for consolidating it. The city of Ploieşti does have a good stadium, with floodlights, the one of ASTRA (which changed name to CSM Ploieşti and plays in Liga III), but it doesn't seem right for Petrolul to play on their rival's ground, even though the rivalry isn't that great. It's just not natural. Plus, the football they play is not that great.
I can understand why FC Braşov is wanted in Liga I (recent investments, relatively important team, big city), but FC Argeş, Jiul or FCM Bacău? OK, Argeş did win the championship sometime before I was born

The only teams I would really like to see back are Sportul Studenţesc and Progresul (ex-FC Naţional), even though they have less fans combined than the population of a small village. It's their style that I miss the most.
From other countries: Shelbourne (I still can't believe how the Irish FA relegated them), Southampton, Bastia, Hapoel Haifa.